The sense of taste is the primary sensory system that determines whether a food or beverage will be ingested or rejected. Taste also influences food processing by the digestive system. Consequently, understanding the mechanisms underlying this sense is central to our ability to control intake of nutrients and to modulate the excesses of consumption that may underlie diseases such as obesity, hypertension and the metabolic syndrome. Our approach to advancing understanding of taste perception has been to use mouse models to identify genes involved in perception. We first identify natural variation in behavioral responses to taste stimuli in inbred mouse strains and then use this information to locate and identify the genes responsible for this variation. This approach, sometimes called positional cloning, is capable of detecting genes involved in all stages of taste perception, from reception in taste bud cells to brain functions responsible for behavioral responses to taste stimuli. In our previous studies, which were the first successful use of positional cloning to identify a functional gene involved in mammalian behavior, we identified and characterized a locus that codes for a sweet taste receptor. In the current comprehensive proposal, we describe studies designed to continue to identify genes involved in behavioral responses to sweet compounds. We also propose to expand our scope to include sour taste-related genes. This positional cloning approach will be complemented with behavioral analyses of physiological mechanisms underlying effects of individual genes. These studies, when completed, may provide important new avenues for interventions designed to modify excess food consumption.